On-farm Evaluation of Optical Sensor Technology for Variable Rate N Application to Corn in Ontario and Quebec
Bao-Luo Ma, and Nicolas Tremblay
Eastern Cereal and Oilseed Research Centre, Ottawa, ON
613-759-1521, [email protected]
Canada
Introduction - Nitrogen
Fertilizer N represents the most costly input in grain cereal production, especially corn
Producers have to balance crop N needs while minimizing N losses via leaching, emission and runoff
NUE is low, about 50%
Soil physical, chemical and biological conditions tremendously affect NUE
N losses as NO3 to surface and ground water, as N2O and NH3 gases to the atmosphere
Annual Quantitative N Cycle for Corn/Soil/Atmosphere (kg N/ha)
Atmospheric N
Corn Crop N (Grain=123;Stover=61; Roots=22)
HN4-N+ NO3-N
-
Fertilizer N
Soil Organic N(6000)
14
120
83
10 2410
192
24
252
23150
14
Grain YieldGrain Yield
ChlorophyllChlorophyll NitrogenNitrogen
The basic relationshipThe basic relationship
Canopy reflectance x Nitrogen LevelCanopy reflectance x Nitrogen Level
Wavelength Wavelength (nm)(nm)
Refl
ecta
nce (
%)
Refl
ecta
nce (
%) High N
Low N
0
5
10
15
20
25
30
35
40
400 500 600 700 800 900
< N < chlorophyll= > reflectance< N < chlorophyll= > reflectance
> N > DW > LA= > reflectance> N > DW > LA= > reflectance
Critical levelsCritical levels
Figure 1 – Chlorophyll meter mesurements in four corn development stages(Argenta, 2001).
45,4
52,1
55,3
58,0
V3V3
Development stagesDevelopment stagesV6V6 V10V10
Sp
ad
Sp
ad
44
46
48
50
52
54
56
58
60
15 25 35 45 55 65 75
SilkingSilking
45,445,4
52,152,1
55,355,3
58,058,0Y = 33,928 + 0,654x - 0,004xY = 33,928 + 0,654x - 0,004x2 2 R R22= 0,98= 0,98
Suficiency index (SI):Suficiency index (SI):
SI =SI = NDVI in the high N reference stripNDVI in the high N reference strip
NDVI in the fieldNDVI in the field
Strip
Corn field
= 0.95= 0.95
ETAA Project Objectives
• To develop a crop-based indicator for corn N management that accounts for spatial variability;
• To determine if the new vehicle based optical sensing technology is sufficiently robust and practical for on-farm use;
• To determine if variable rate N application based on spectral reflectance can improve NUE and corn performance on a farm scale.
ETAA Variable Rate Nitrogen Study - 2005
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5 3 2 1 6 9 4
7
9
7
8
o
30+60
o +o + +o +
8
3 4 5 6 1 2 6 5 1 7 3 4 2 2 9 5 4 6 39 1
7 9 7
10 8 10 10
16 26
33
34
2515
+o
+o +o
+o +o
+ooo
o
o
o o o
o
+ + + +
17 27 35
1 2 3 4 5 6 10 11 12 13 14 18 19 20 21 22 23 24 28 29 30 31 32 36 37 38 39 40
Rep 1 Rep 2 Rep 3 Rep 4North
30ft
960ft = 292.6 m
Nitrogen Rates
1) 0 kg N/ha preplant2) 30 kg N/ha preplant (26.7 lb/acre)3) 60 kg N/ha preplant (53.4 lb/acre)4) 90 kg N/ha preplant (80.1 lb/acre)5) 120 kg N/ha preplant (106.8 lb/acre)6) 150 kg N/ha preplant (133.5 lb/acre)7) 30 kg N/ha preplant + 30 kg N/ha sidedress at V68) 30 kg N/ha preplant + 60 kg N/ha sidedress at V69) 30 kg N/ha preplant + 90 kg N/ha sidedress at V6
10) 30 kg N/ha preplant + 120 kg N/ha sidedress at V6* 30 kg N/ha preplant + variable rate N at V6
Hybrid
Pioneer 39D 80 (2550 CHU)- (Roundup Ready + Poncho 250)
Nitrogen Type
1) Urea (46-0-0) broadcast preplant
2) Urea (46-0-0) sidedressed at V6
Dimensions12 rows per plot
30" rowsplot width = 30 ft
plot length = 80 m (for treatments 1-6),20 m (for treatments 7-10)
Total Area
2.34 ha = 5.8 acres
Revised June 29, 2005
30+60 30+120 30+120
Applied N dose (kg N ha-1) Contrast analysis
0 30 60 90 120 150 Linear Quadratic Residual
NDVI_NS a 30DAS 0.35 0.40 0.43 0.43 0.43 0.41*
(41%) b
**(57%)
NS
NDVI_GS a
26DAS 0.35 0.37 0.40 0.38 0.40 0.37*
(18%)**
(58%)NS
33DAS 0.42 0.46 0.48 0.48 0.50 0.47*
(47%)*
(44%)NS
Responses of NDVI_GS and NDVI_NS to fertilizer N rates
y = 0.0008x + 0.35
R2 = 0.74
0.30
0.35
0.40
0.45
0.50
0.55
0 30 60 90 120 150
Fertilizer N preplant (kg N ha-1)
Can
opy
refle
ctan
ce (N
DV
I)GreenSeeker measures canopy differences at pre-sidedress (2005)
Saturation index shows seasonal N needs (Qc data)
R2 = 0.750
2
4
6
8
10
75 80 85 90 95 100 105
Saturation index (%)
Yie
ld d
iffe
renc
e du
e to
N (
t/ha
)
Grain yield
0 30 60 90 120 150 30+30 30+60 30+90 30+120 Variable
Fertilizer rate (kg N/ha)
0
2
4
6
8
10
12
14
16
Gra
in y
ield
(Mg/
ha)
** *
y = -0.0002x2 + 0.077x + 7.3
R2 = 0.979
y = -0.0002x2 + 0.066x + 7.3
R 2 = 0.995
6789
101112131415
0 30 60 90 120 150
Fertilizer (kg N ha-1)
Gra
in y
ield
(M
g h
a-1)
Preplant 30+sidedress
ETAA Variable Rate Nitrogen Study - 2006 Revised: May 10, 2006
600 ft
9 N
49
71000 ft
48 76 2 5 12 11 1 4 3 1 38
o10 3 8 6 5 12 11 1 2 1 4+o 37 600 ft
47
o 936
8 +o+ + +o 10 + +o +
52 51 50 46 45 44 43 42 41 40 39 35 34 33 32 31 30 29 28 27
Rep 4 Rep 350 ft
-30 ft- Rep 1 Rep 21 2 3 4 5 6 7 8 9 13 14 15 19 20 21 22 23 24 25 26
+o + + 10 + + +o+o 8
10
5 3 1 11 12 1 6 4 8 2 o600 ft o 16
11
9 101000 ft
12 +o7 6 17 3 4 12 11 1 1 2 5
7
18
9
Nitrogen Rates1) 0 kg N/ha preplant2) 30 kg N/ha preplant (26.7 lb/acre)3) 60 kg N/ha preplant (53.4 lb/acre) Hybrid4) 90 kg N/ha preplant (80.1 lb/acre) Pioneer 39D80 (2550 CHU)5) 120 kg N/ha preplant (106.8 lb/acre) - (Roundup Ready + Poncho 1250)6) 150 kg N/ha preplant (133.5 lb/acre)7) 30 kg N/ha preplant + 30 kg N/ha sidedress at V6 Nitrogen Type8) 30 kg N/ha preplant + 60 kg N/ha sidedress at V6 1) Urea (46-0-0) broadcast preplant9) 30 kg N/ha preplant + 90 kg N/ha sidedress at V6 2) UAN (28-0-0) sidedressed at V610) 30 kg N/ha preplant + 120 kg N/ha sidedress at V611) Variable rate - 30 kg N/ha preplant + variable rate N at V6 Note: the variable rate plots are surounded on either side by a 0 N plot and 180 kg N/h plot12) 180 kg N/ha preplant
Adjustable Sensor Mounting
Ottawa Equipment
• Ford 7610 tractor with modified hydraulic returns• Yetter 2995 Bubble Fertilizer Coulters with rear Knife• 250 liter tank with filter• John Blue positive displacement piston pump with flow divider• Rawson Accurate Controller• Dickey John Radar• Raven GPS• GreenSeeker RT200
GreenSeeker MappingJune 26, 2006
REP AVG MAX MIN
1 .57 .78 .32
2 .51 .76 .25
3 .58 .83 .26
4 .66 .85 .32
Corn 32” to 36” high on Application Day, Ottawa
Ottawa Application
• Non-irrigated spring wheat with modified inputs gave a very reasonable application curve
• On application day the curve could not be manipulated to suite our rates because of high NDVI values.
• Only choice we had was to use the 16 point stepped (not interpolated) graph
• In StJean, the non-irrigated spring wheat was manipulated to give a very reasonable curve
Ottawa Rate
NDVI US gal/ac
.2 0
.25 0
.3 0
.35 0
.4 0
.45 0
.5 0
.55 9.2
.6 35.9
.65 35.0
.7 33.1
.75 32.1
.8 28.5
.85 21.2
.9 11.0
.95 9.2
Accurate controller settings:9.2 to 36.8 gal /ac was the preset range(30 kg N/ha to 120 kg N/ha)Controller works on percentage change from a mid point.23 gal/ac as the mid point with 4 % increment giving .92 galThere are 32 increments.
Summary (2005)
• Very high grain yield in 2005; yield did not plateau;
• Yield was more responsive to sidedress (77 kg/kg N) than preplant (66 kg/kg N) fertilizer N;
• Canopy reflectance (NDVI) differentiate low from high soil N
• NDVI ranges are narrow, sensitive with crop growth stage
• Better economic return with sidedressed fertilizer N. But, further research is needed for variable N rate application.
Summary (2006)• First year of variable rate N application based on NDVI saturation
index (SI)• Canopy NDVI values change rapidly from V6 to V8 (plants 2.5-3
feet tall) and can be quickly saturated (NDVI >0.82).• The rainfed spring wheat algorithm provided by the RT-200
GreenSeeker was used in Quebec where NDVIref <0.7• In Ottawa site, differences in canopy reflectance among preplant
broadcast fertilizer N rates was confounded with poor seedling growth under high N rates due to low soil pH coupled with cool spring.
• Although such confounding effect was minimal around or after sidedress, it made difficult interpret the NDVI data.
• The maximum NDVI value was used to derive SI, and Nmin and Nmax were set at 9.2 and 36.8 gal/ac; variable N rate application was made using the 16 points algorithm.
• It is expected that a better NDVI-N requirement algorithm will be available or developed at site for use next year.
Acknowledgements
Ontario Soil and Crop Improvement Association
Lynne Evenson, Doug Balchin,
Vivianne Deslauriers